<!DOCTYPE html>
<html>
<body>
<div id="menubar" role="menubar" tabindex="0" aria-activedescendant="file">
  <span id="file" role="menuitem" aria-expanded="false">File</span>
  <span id="edit" role="menuitem" aria-expanded="false">Edit</span>
</div>
<script>
  var menubar = document.getElementById('menubar');
  menubar.focus();
  function go() {
    menubar.setAttribute('aria-activedescendant', 'edit');
  }
</script>
</body>
</html>
